Infrared Radiation Statistics of Nonluminous Turbulent Diffusion Flames

Mixture fraction and radiation statistics were studied for radiation paths through turbulent carbon monoxide/hydrogen diffusion flames burning in still air. Measurements included Mie scattering for mixture fraction statistics and fast-response infrared spectroscopy for radiation statistics. Measured mixture fraction statistics also were used to predict radiation statistics based on stochastic time series methods, the laminar flamelet approximation, and a narrow-band radiation model. Measured intensities of radiation fluctuations were in the range 10–40 percent, which causes mean radiation levels to be 1.1–4.2 times larger than estimates based on mean scalar properties in the flames. In contrast, stochastic predictions of mean and fluctuating radiation properties were generally in excellent agreement with measurements. An exception was the temporal integral scales of radiation fluctuations, where differential diffusion errors of the Mie scattering measurements were identified as the source of the discrepancies.